[dustcoin]

This is false information that is commonly repeated. The ships produce more of a particular pollutant, sulfur dioxide (SO2), not CO2. Personal vehicles produce barely any SO2 (gasoline contains no sulfur, diesel contains a small amount) so it isn't surprising a few container ships, which burn sulfur-heavy bunker fuel, produce more.

[Gibbon1]

I always want to think of sulfur in HFO are contributing to the total heating value because the stuff used to be 3% sulfur. Realistically it's probably 1%. Sulfur only has about 1/3 the energy content as HFO.

But they are phasing out high sulfur HFO in 2020 I think ships are restricted to 0.5% sulfur.